In the field of conveying technology, among the conveyor belts that are known are pouch conveyor belts, which are also referred to as pouch conveyors or bag conveyors or are known under the trade name Sicon® belts. They derive their name from the structure of the conveyor belt, which transports the material it conveys in a closed manner by being folded into a loop or pouch. The ends of the belt have profiles with vulcanized-in reinforcing elements, such as for example steel cables, and serve for the guiding of the belt by means of the guide and support rollers. The reinforcing elements take over the tensile forces of the belt. They are arranged one above the other in a vertical axis. The middle part of the pouch conveyor belt that carries the material being conveyed is of highly elastic rubber and is free from reinforcing elements and other stiffening elements.
On account of this structural design of the pouch conveyor belt and the corresponding plant technology, small curve radii are made possible, as a result of which transfer stations are avoided and the pouch conveyor belt can transport the material being conveyed in a closed manner from the feed point to the discharge point. This avoids environmental impact of the material being conveyed, for example due to dust, spillage etc., and conversely protects the material being conveyed from environmental influences, such as for example wind, rain, solar irradiation, etc. The belt is also closed on the return side. The reinforcing elements arranged one above the other in the vertical axis ensure that they always have the same radius, even in curves of up to 180°. These properties result in a highly dynamic conveying system that makes small radii, steep gradients and high levels of acceleration possible, for example for use in a confined space, such as in factories, on ships, in steelworks, etc. Examples of such pouch conveyor belts or pouch conveying installations are disclosed for example by WO 89/12593 and EP 0 765 287 B1.
However, these properties of the conveying system also result in corresponding requirements for the dynamic properties of the corresponding pouch conveyor belt with regard to its structure and its materials. Thus, the pouch conveyor belt must be designed in such a way that it withstands undamaged for as long as possible the dynamic requirements due to acceleration and retardation as well as bending and compression, since the failure of a conveying installation leads to great problems and costs, as does the exchange of a conveyor belt, which has to be performed over the entire length of the conveying installation. In this respect, long-term loading tests have shown that the dynamic loads, in particular due to the bending and compression of the conveyor belt as a result of the opening and closing during loading and unloading, cause damage in the form of microcracks to occur on the surface of the pouch conveyor belt, and then penetrate into the material of the belt. These microcracks occur in particular at the bending point of the pouch conveyor belt, i.e. at the lowest point of the loop, which bears the greatest load in terms of the weight of the material being conveyed and is subjected to the greatest loading as a result of the opening and closing of the conveyor belt, and tend to occur on the outer side of the pouch conveyor belt, i.e. on the side facing away from the material being conveyed.
In order to satisfy these dynamic requirements, rubbers, such as for example butyl or nitrile or chloroprene rubber mixes, are generally used for pouch conveyor belts. In addition, these rubber mixes often also contain between 10 and 60 phr of plasticizer.
Apart from the dynamic requirements, there may at the same time also be further requirements for pouch conveyor belts, such as for example a certain flame resistance, which in the case of use underground for example may be prescribed for safety reasons.
With regard to the flame resistance, chloroprene or styrene rubber mixes are particularly well suited.
DE 10 2009 043 904 A1 describes a troughed conveyor belt with a vulcanizable rubber mix on the basis of inter alia chloroprene rubber (CR), which is distinguished by its high flame, weathering and aging resistance, in particular for conveyor belts for use underground.
CN 202642653 U describes a tubular conveyor belt for underground coal mining with an aramid structural layer, which is arranged between an upper flame-resistant bonding layer and a lower flame-resistant bonding layer.
CN 102642693 A describes a flame-resistant tubular conveyor belt for coal mines with a skeleton layer, which is arranged between an upper flame-resistant bonding layer and a lower flame-resistant bonding layer.
These flame-resistant troughed and tubular conveyor belts share the common feature that these types of conveyor belts are subjected to much lower dynamic loads in comparison with pouch conveyor belts, because the tensile forces of the belts are transmitted through reinforcing elements that extend in the longitudinal direction, i.e. in the conveying or running direction, and are generally arranged in a distributed manner over the width of the conveyor belt. As a result of this structure, smaller gradients, curve radii and accelerations apply to troughed and tubular conveyor belts than to pouch conveyor belts, so that on the one hand there is no need to use materials that satisfy dynamic requirements as in the case of pouch conveyor belts, and on the other hand flame-resistant materials such as those described above can be used. Since, however, on account of their comparatively high filler content, flame-resistant materials do not have the necessary flexibility to satisfy the dynamic requirements of a pouch conveyor belt, these materials cannot be transferred from the flame-resistant troughed and tubular conveyor belts to pouch conveyor belts.